Field of the Invention
The present invention relates to a method for manufacturing a liquid ejection head mounted on a liquid ejection apparatus, and a configuration of a liquid ejection head.
Description of the Related Art
An ordinary liquid ejection apparatus is provided with a liquid ejection head mounted on a carriage, a carriage driving means, a recording medium conveying means, and a control means for controlling these components. A recording operation conducted while moving the carriage is referred to as a serial scanning method. Japanese Patent No 3801003 discloses a serial scanning liquid ejection head. The disclosed liquid ejection head has a housing provided with a liquid chamber which supplies a liquid to ejection ports. The liquid ejection head has six liquid chambers adjoining in a scanning direction, and a plurality of ejection ports each corresponding to each of the liquid chambers.
To increase a recording rate of serial scanning liquid ejection head, it is effective to increase the number of ejection ports (a length of an ejection port array) in a direction to cross a scanning direction of the liquid ejection head (hereafter, “cross direction”). This can increase a recordable width in the cross direction in one scanning event.
In a liquid ejection head, a recovery operation for removing a thickened matter or accumulated air bubbles in the liquid, such as ink, in the liquid ejection head, is usually conducted to maintain high recording quality. To discharge the thickened matter or the accumulated air bubbles reliably, the liquid contained in the liquid chambers is also discharged. As the number of ejection ports increases, an amount of liquid to be discharged also increases. Therefore, the volume of the liquid chambers needs to be increased to reduce the frequency at which the recovery operation is conducted. As the number of ejection ports increases, air bubbles generated during the recording operation also increases inevitably. Since the air bubbles are partially accumulated in the liquid chambers, the volume of the liquid chambers needs to be increased to accommodate the air bubbles in the liquid chambers.
Regarding a housing of the liquid ejection head, to reduce cost and to form a channel toward the printing element board, a plurality of liquid chambers are usually formed with their widths in the scanning direction decreasing toward the ejection ports. The liquid chambers, as described above, desirably have a greater volume to contain the liquid and to accumulate air bubbles. Therefore, the liquid chambers tend to be elongated in shape in the cross direction. This enables the air bubbles generated near the ejection ports to be moved smoothly to the liquid chambers.
The housing constituting the liquid chamber is usually manufactured by molding. In the liquid ejection head disclosed in Japanese Patent No. 3801003, to form the liquid chambers, six mold pieces to be drawn in the same direction are used. The mold piece has a draft from the viewpoint of releasability during molding. Specifically, the width of the mold piece in the scanning direction decreases gradually toward an end portion from a base portion, and the mold piece is drawn from the base portion after molding. Partition walls between the liquid chambers adjoining in the scanning direction are formed by gaps of the mold pieces. However, with the draft, the thickness of the partition wall in the scanning direction becomes greater at the end portion of the mold piece and becomes smaller at the base portion, whereby becomes uneven in the cross direction. Since the liquid chambers tend to be elongated in the cross direction as described above, the mold pieces are elongated and unevenness in the thickness of the partition walls in the cross direction becomes more significant. In molding, if the width of the product wall is uneven, problems like sink and short circuit may easily occur.